19 - Expression and Properties of Rab7 in Endosome Function

Late endocytic membrane transport is a complex process involving sorting of molecules internalized from the cell surface or delivered from the exocytic pathway, recycling of molecules to the trans-Golgi, and flux of molecules to and from lysosomes. It appears that there are multiple intersection points between the exocytic and endocytic pathways, molecules may transit to and from lysosomes by both vesicular and nonvesicular routes and protein and lipid sorting depends on the dynamic formation of multivesicular bodies. The elucidation of these events at the molecular level is being realized through the combined application of genetic, biochemical, and morphologic approaches in both yeast and mammalian cells. Assays described in this chapter are useful for monitoring individual late endocytic events and elucidating their regulation by Rab7 and associated factors. Thus, they contribute to the growing arsenal of tools available for pinpointing the site of action of regulatory factors or testing the involvement of particular membrane compartments in a given biologic process.